﻿/*
**  Collision类
*/
if (!$.Engine.Collision || typeof $.Engine.Collision === "undefined") $.Engine.Collision = {};
// Find the separation between poly1 and poly2 for a give edge normal on poly1.
// Find the max separation between poly1 and poly2 using edge normals
// Find edge normal of max separation on A - return if separating axis is found
// Find edge normal of max separation on B - return if separation axis is found
// Choose reference edge(minA, minB)
// Find incident edge
// Clip
// The normal points from 1 to 2
// from poly1.
$.Engine.Collision.Collision = function(){};
$.extend($.Engine.Collision.Collision, {
  nullFeature: 0x000000ff,
  ClipSegmentToLine: function (vOut, vIn, normal, offset) {
    // Start with no output points
    var numOut = 0;

    var vIn0 = vIn[0].v;
    var vIn1 = vIn[1].v;

    // Calculate the distance of end points to the line
    var distance0 = $.Engine.Math.Dot(normal, vIn[0].v) - offset;
    var distance1 = $.Engine.Math.Dot(normal, vIn[1].v) - offset;

    // If the points are behind the plane
    if (distance0 <= 0.0) vOut[numOut++] = vIn[0];
    if (distance1 <= 0.0) vOut[numOut++] = vIn[1];

    // If the points are on different sides of the plane
    if (distance0 * distance1 < 0.0) {
      // Find intersection point of edge and plane
      var interp = distance0 / (distance0 - distance1);
      // expanded for performance
      var tVec = vOut[numOut].v;
      tVec.x = vIn0.x + interp * (vIn1.x - vIn0.x);
      tVec.y = vIn0.y + interp * (vIn1.y - vIn0.y);
      if (distance0 > 0.0) {
        vOut[numOut].id = vIn[0].id;
      }
      else {
        vOut[numOut].id = vIn[1].id;
      }
      ++numOut;
    }

    return numOut;
  },

  EdgeSeparation: function (poly1, edge1, poly2) {
    var vert1s = poly1.m_vertices;
    var count2 = poly2.m_vertexCount;
    var vert2s = poly2.m_vertices;

    // Convert normal from into poly2's frame.
    //b2Settings.b2Assert(edge1 < poly1.m_vertexCount);

    //var normal = $.Engine.Math.MulMV(poly1.m_R, poly1->m_normals[edge1]);
    var normalX = poly1.m_normals[edge1].x;
    var normalY = poly1.m_normals[edge1].y;
    var tX = normalX;
    var tMat = poly1.m_R;
    normalX = tMat.col1.x * tX + tMat.col2.x * normalY;
    normalY = tMat.col1.y * tX + tMat.col2.y * normalY;
    // ^^^^^^^ normal.MulM(poly1.m_R);

    //var normalLocal2 = $.Engine.Math.MulTMV(poly2.m_R, normal);
    var normalLocal2X = normalX;
    var normalLocal2Y = normalY;
    tMat = poly2.m_R;
    tX = normalLocal2X * tMat.col1.x + normalLocal2Y * tMat.col1.y;
    normalLocal2Y = normalLocal2X * tMat.col2.x + normalLocal2Y * tMat.col2.y;
    normalLocal2X = tX;
    // ^^^^^ normalLocal2.MulTM(poly2.m_R);

    // Find support vertex on poly2 for -normal.
    var vertexIndex2 = 0;
    var minDot = Number.MAX_VALUE;
    for (var i = 0; i < count2; ++i) {
      //var dot = $.Engine.Math.Dot(vert2s[i], normalLocal2);
      var tVec = vert2s[i];
      var dot = tVec.x * normalLocal2X + tVec.y * normalLocal2Y;
      if (dot < minDot) {
        minDot = dot;
        vertexIndex2 = i;
      }
    }

    //b2Vec2 v1 = poly1->m_position + b2Mul(poly1->m_R, vert1s[edge1]);
    tMat = poly1.m_R;
    var v1X = poly1.m_position.x + (tMat.col1.x * vert1s[edge1].x + tMat.col2.x * vert1s[edge1].y)
    var v1Y = poly1.m_position.y + (tMat.col1.y * vert1s[edge1].x + tMat.col2.y * vert1s[edge1].y)

    //b2Vec2 v2 = poly2->m_position + b2Mul(poly2->m_R, vert2s[vertexIndex2]);
    tMat = poly2.m_R;
    var v2X = poly2.m_position.x + (tMat.col1.x * vert2s[vertexIndex2].x + tMat.col2.x * vert2s[vertexIndex2].y)
    var v2Y = poly2.m_position.y + (tMat.col1.y * vert2s[vertexIndex2].x + tMat.col2.y * vert2s[vertexIndex2].y)

    //var separation = $.Engine.Math.Dot( b2Math.SubtractVV( v2, v1 ) , normal);
    v2X -= v1X;
    v2Y -= v1Y;
    //var separation = $.Engine.Math.Dot( v2 , normal);
    var separation = v2X * normalX + v2Y * normalY;
    return separation;
  },

  FindMaxSeparation: function (edgeIndex /*int ptr*/, poly1, poly2, conservative) {
    var count1 = poly1.m_vertexCount;

    // Vector pointing from the origin of poly1 to the origin of poly2.
    //var d = b2Math.SubtractVV( poly2.m_position, poly1.m_position );
    var dX = poly2.m_position.x - poly1.m_position.x;
    var dY = poly2.m_position.y - poly1.m_position.y;

    //var dLocal1 = $.Engine.Math.MulTMV(poly1.m_R, d);
    var dLocal1X = (dX * poly1.m_R.col1.x + dY * poly1.m_R.col1.y);
    var dLocal1Y = (dX * poly1.m_R.col2.x + dY * poly1.m_R.col2.y);

    // Get support vertex hint for our search
    var edge = 0;
    var maxDot = -Number.MAX_VALUE;
    for (var i = 0; i < count1; ++i) {
      //var dot = $.Engine.Math.Dot(poly.m_normals[i], dLocal1);
      var dot = (poly1.m_normals[i].x * dLocal1X + poly1.m_normals[i].y * dLocal1Y);
      if (dot > maxDot) {
        maxDot = dot;
        edge = i;
      }
    }

    // Get the separation for the edge normal.
    var s = $.Engine.Collision.Collision.EdgeSeparation(poly1, edge, poly2);
    if (s > 0.0 && conservative == false) {
      return s;
    }

    // Check the separation for the neighboring edges.
    var prevEdge = edge - 1 >= 0 ? edge - 1 : count1 - 1;
    var sPrev = $.Engine.Collision.Collision.EdgeSeparation(poly1, prevEdge, poly2);
    if (sPrev > 0.0 && conservative == false) {
      return sPrev;
    }

    var nextEdge = edge + 1 < count1 ? edge + 1 : 0;
    var sNext = $.Engine.Collision.Collision.EdgeSeparation(poly1, nextEdge, poly2);
    if (sNext > 0.0 && conservative == false) {
      return sNext;
    }

    // Find the best edge and the search direction.
    var bestEdge = 0;
    var bestSeparation;
    var increment = 0;
    if (sPrev > s && sPrev > sNext) {
      increment = -1;
      bestEdge = prevEdge;
      bestSeparation = sPrev;
    }
    else if (sNext > s) {
      increment = 1;
      bestEdge = nextEdge;
      bestSeparation = sNext;
    }
    else {
      // pointer out
      edgeIndex[0] = edge;
      return s;
    }

    while (true) {

      if (increment == -1)
        edge = bestEdge - 1 >= 0 ? bestEdge - 1 : count1 - 1;
      else
        edge = bestEdge + 1 < count1 ? bestEdge + 1 : 0;

      s = $.Engine.Collision.Collision.EdgeSeparation(poly1, edge, poly2);
      if (s > 0.0 && conservative == false) {
        return s;
      }

      if (s > bestSeparation) {
        bestEdge = edge;
        bestSeparation = s;
      }
      else {
        break;
      }
    }

    // pointer out
    edgeIndex[0] = bestEdge;
    return bestSeparation;
  },

  FindIncidentEdge: function (c, poly1, edge1, poly2) {
    var count1 = poly1.m_vertexCount;
    var vert1s = poly1.m_vertices;
    var count2 = poly2.m_vertexCount;
    var vert2s = poly2.m_vertices;

    // Get the vertices associated with edge1.
    var vertex11 = edge1;
    var vertex12 = edge1 + 1 == count1 ? 0 : edge1 + 1;

    // Get the normal of edge1.
    var tVec = vert1s[vertex12];
    //var normal1Local1 = $.Engine.Math.CrossVF( b2Math.SubtractVV( vert1s[vertex12], vert1s[vertex11] ), 1.0);
    var normal1Local1X = tVec.x;
    var normal1Local1Y = tVec.y;
    tVec = vert1s[vertex11];
    normal1Local1X -= tVec.x;
    normal1Local1Y -= tVec.y;
    var tX = normal1Local1X;
    normal1Local1X = normal1Local1Y;
    normal1Local1Y = -tX;
    // ^^^^ normal1Local1.CrossVF(1.0);

    var invLength = 1.0 / Math.sqrt(normal1Local1X * normal1Local1X + normal1Local1Y * normal1Local1Y);
    normal1Local1X *= invLength;
    normal1Local1Y *= invLength;
    // ^^^^normal1Local1.Normalize();
    //var normal1 = $.Engine.Math.MulMV(poly1.m_R, normal1Local1);
    var normal1X = normal1Local1X;
    var normal1Y = normal1Local1Y;

    tX = normal1X;
    var tMat = poly1.m_R;
    normal1X = tMat.col1.x * tX + tMat.col2.x * normal1Y;
    normal1Y = tMat.col1.y * tX + tMat.col2.y * normal1Y;
    // ^^^^ normal1.MulM(poly1.m_R);

    //var normal1Local2 = $.Engine.Math.MulTMV(poly2.m_R, normal1);
    var normal1Local2X = normal1X;
    var normal1Local2Y = normal1Y;
    tMat = poly2.m_R;
    tX = normal1Local2X * tMat.col1.x + normal1Local2Y * tMat.col1.y;
    normal1Local2Y = normal1Local2X * tMat.col2.x + normal1Local2Y * tMat.col2.y;
    normal1Local2X = tX;
    // ^^^^ normal1Local2.MulTM(poly2.m_R);

    // Find the incident edge on poly2.
    var vertex21 = 0;
    var vertex22 = 0;
    var minDot = Number.MAX_VALUE;
    for (var i = 0; i < count2; ++i) {
      var i1 = i;
      var i2 = i + 1 < count2 ? i + 1 : 0;

      //var normal2Local2 = $.Engine.Math.CrossVF( b2Math.SubtractVV( vert2s[i2], vert2s[i1] ), 1.0);
      tVec = vert2s[i2];
      var normal2Local2X = tVec.x;
      var normal2Local2Y = tVec.y;
      tVec = vert2s[i1];
      normal2Local2X -= tVec.x;
      normal2Local2Y -= tVec.y;
      tX = normal2Local2X;
      normal2Local2X = normal2Local2Y;
      normal2Local2Y = -tX;
      // ^^^^ normal2Local2.CrossVF(1.0);

      invLength = 1.0 / Math.sqrt(normal2Local2X * normal2Local2X + normal2Local2Y * normal2Local2Y);
      normal2Local2X *= invLength;
      normal2Local2Y *= invLength;
      // ^^^^ normal2Local2.Normalize();

      //var dot = $.Engine.Math.Dot(normal2Local2, normal1Local2);
      var dot = normal2Local2X * normal1Local2X + normal2Local2Y * normal1Local2Y;
      if (dot < minDot) {
        minDot = dot;
        vertex21 = i1;
        vertex22 = i2;
      }
    }

    var tClip;
    // Build the clip vertices for the incident edge.
    tClip = c[0];
    //tClip.v = b2Math.AddVV(poly2.m_position, $.Engine.Math.MulMV(poly2.m_R, vert2s[vertex21]));
    tVec = tClip.v;
    tVec.SetV(vert2s[vertex21]);
    tVec.MulM(poly2.m_R);
    tVec.Add(poly2.m_position);

    tClip.id.features.referenceFace = edge1;
    tClip.id.features.incidentEdge = vertex21;
    tClip.id.features.incidentVertex = vertex21;

    tClip = c[1];
    //tClip.v = b2Math.AddVV(poly2.m_position, $.Engine.Math.MulMV(poly2.m_R, vert2s[vertex22]));
    tVec = tClip.v;
    tVec.SetV(vert2s[vertex22]);
    tVec.MulM(poly2.m_R);
    tVec.Add(poly2.m_position);
    tClip.id.features.referenceFace = edge1;
    tClip.id.features.incidentEdge = vertex21;
    tClip.id.features.incidentVertex = vertex22;
  },

  CollidePolyTempVec: new $.Engine.Math.Vector2D(),
  CollidePoly: function (manifold, polyA, polyB, conservative) {
    manifold.pointCount = 0;

    var edgeA = 0;
    var edgeAOut = [edgeA];
    var separationA = $.Engine.Collision.Collision.FindMaxSeparation(edgeAOut, polyA, polyB, conservative);
    edgeA = edgeAOut[0];
    if (separationA > 0.0 && conservative == false)
      return;

    var edgeB = 0;
    var edgeBOut = [edgeB];
    var separationB = $.Engine.Collision.Collision.FindMaxSeparation(edgeBOut, polyB, polyA, conservative);
    edgeB = edgeBOut[0];
    if (separationB > 0.0 && conservative == false)
      return;

    var poly1;
    var poly2;
    var edge1 = 0;
    var flip = 0;
    var k_relativeTol = 0.98;
    var k_absoluteTol = 0.001;

    // TODO_ERIN use "radius" of poly for absolute tolerance.
    if (separationB > k_relativeTol * separationA + k_absoluteTol) {
      poly1 = polyB;
      poly2 = polyA;
      edge1 = edgeB;
      flip = 1;
    }
    else {
      poly1 = polyA;
      poly2 = polyB;
      edge1 = edgeA;
      flip = 0;
    }

    var incidentEdge = [new $.Engine.Collision.ClipVertex(), new $.Engine.Collision.ClipVertex()];
    $.Engine.Collision.Collision.FindIncidentEdge(incidentEdge, poly1, edge1, poly2);

    var count1 = poly1.m_vertexCount;
    var vert1s = poly1.m_vertices;

    var v11 = vert1s[edge1];
    var v12 = edge1 + 1 < count1 ? vert1s[edge1 + 1] : vert1s[0];

    //var dv = b2Math.SubtractVV(v12, v11);
    var dvX = v12.x - v11.x;
    var dvY = v12.y - v11.y;

    //var sideNormal = $.Engine.Math.MulMV(poly1.m_R, b2Math.SubtractVV(v12, v11));
    var sideNormalX = v12.x - v11.x;
    var sideNormalY = v12.y - v11.y;

    var tX = sideNormalX;
    var tMat = poly1.m_R;
    sideNormalX = tMat.col1.x * tX + tMat.col2.x * sideNormalY;
    sideNormalY = tMat.col1.y * tX + tMat.col2.y * sideNormalY;
    // ^^^^ sideNormal.MulM(poly1.m_R);

    var invLength = 1.0 / Math.sqrt(sideNormalX * sideNormalX + sideNormalY * sideNormalY);
    sideNormalX *= invLength;
    sideNormalY *= invLength;
    // ^^^^ sideNormal.Normalize();

    //var frontNormal = $.Engine.Math.CrossVF(sideNormal, 1.0);
    var frontNormalX = sideNormalX;
    var frontNormalY = sideNormalY;
    tX = frontNormalX;
    frontNormalX = frontNormalY;
    frontNormalY = -tX;
    // ^^^^ frontNormal.CrossVF(1.0);

    // Expanded for performance
    //v11 = b2Math.AddVV(poly1.m_position, $.Engine.Math.MulMV(poly1.m_R, v11));
    var v11X = v11.x;
    var v11Y = v11.y;
    tX = v11X;
    tMat = poly1.m_R;
    v11X = tMat.col1.x * tX + tMat.col2.x * v11Y;
    v11Y = tMat.col1.y * tX + tMat.col2.y * v11Y;
    // ^^^^ v11.MulM(poly1.m_R);
    v11X += poly1.m_position.x;
    v11Y += poly1.m_position.y;
    //v12 = b2Math.AddVV(poly1.m_position, $.Engine.Math.MulMV(poly1.m_R, v12));
    var v12X = v12.x;
    var v12Y = v12.y;
    tX = v12X;
    tMat = poly1.m_R;
    v12X = tMat.col1.x * tX + tMat.col2.x * v12Y;
    v12Y = tMat.col1.y * tX + tMat.col2.y * v12Y;
    // ^^^^ v12.MulM(poly1.m_R);
    v12X += poly1.m_position.x;
    v12Y += poly1.m_position.y;

    //var frontOffset = $.Engine.Math.Dot(frontNormal, v11);
    var frontOffset = frontNormalX * v11X + frontNormalY * v11Y;
    //var sideOffset1 = -$.Engine.Math.Dot(sideNormal, v11);
    var sideOffset1 = -(sideNormalX * v11X + sideNormalY * v11Y);
    //var sideOffset2 = $.Engine.Math.Dot(sideNormal, v12);
    var sideOffset2 = sideNormalX * v12X + sideNormalY * v12Y;

    // Clip incident edge against extruded edge1 side edges.
    var clipPoints1 = [new $.Engine.Collision.ClipVertex(), new $.Engine.Collision.ClipVertex()];
    var clipPoints2 = [new $.Engine.Collision.ClipVertex(), new $.Engine.Collision.ClipVertex()];

    var np = 0;

    // Clip to box side 1
    $.Engine.Collision.Collision.CollidePolyTempVec.Set(-sideNormalX, -sideNormalY);
    np = $.Engine.Collision.Collision.ClipSegmentToLine(clipPoints1, incidentEdge, $.Engine.Collision.Collision.CollidePolyTempVec, sideOffset1);

    if (np < 2)
      return;

    // Clip to negative box side 1
    $.Engine.Collision.Collision.CollidePolyTempVec.Set(sideNormalX, sideNormalY);
    np = $.Engine.Collision.Collision.ClipSegmentToLine(clipPoints2, clipPoints1, $.Engine.Collision.Collision.CollidePolyTempVec, sideOffset2);

    if (np < 2)
      return;

    // Now clipPoints2 contains the clipped points.
    if (flip) {
      manifold.normal.Set(-frontNormalX, -frontNormalY);
    }
    else {
      manifold.normal.Set(frontNormalX, frontNormalY);
    }
    // ^^^^ manifold.normal = flip ? frontNormal.Negative() : frontNormal;

    var pointCount = 0;
    for (var i = 0; i < $.Engine.Settings.maxManifoldPoints; ++i) {
      //var separation = $.Engine.Math.Dot(frontNormal, clipPoints2[i].v) - frontOffset;
      var tVec = clipPoints2[i].v;
      var separation = (frontNormalX * tVec.x + frontNormalY * tVec.y) - frontOffset;

      if (separation <= 0.0 || conservative == true) {
        var cp = manifold.points[pointCount];
        cp.separation = separation;
        cp.position.SetV(clipPoints2[i].v);
        cp.id.Set(clipPoints2[i].id);
        cp.id.features.flip = flip;
        ++pointCount;
      }
    }

    manifold.pointCount = pointCount;
  }
});
$.Engine.Collision.Collision.CollideCircle = function (manifold, circle1, circle2, conservative) {
  manifold.pointCount = 0;

  //var d = b2Math.SubtractVV(circle2.m_position, circle1.m_position);
  var dX = circle2.m_position.x - circle1.m_position.x;
  var dY = circle2.m_position.y - circle1.m_position.y;
  //var distSqr = $.Engine.Math.Dot(d, d);
  var distSqr = dX * dX + dY * dY;
  var radiusSum = circle1.m_radius + circle2.m_radius;
  if (distSqr > radiusSum * radiusSum && conservative == false) {
    return;
  }

  var separation;
  if (distSqr < Number.MIN_VALUE) {
    separation = -radiusSum;
    manifold.normal.Set(0.0, 1.0);
  }
  else {
    var dist = Math.sqrt(distSqr);
    separation = dist - radiusSum;
    var a = 1.0 / dist;
    manifold.normal.x = a * dX;
    manifold.normal.y = a * dY;
  }

  manifold.pointCount = 1;
  var tPoint = manifold.points[0];
  tPoint.id.set_key(0);
  tPoint.separation = separation;
  //tPoint.position = b2Math.SubtractVV(circle2.m_position, b2Math.MulFV(circle2.m_radius, manifold.normal));
  tPoint.position.x = circle2.m_position.x - (circle2.m_radius * manifold.normal.x);
  tPoint.position.y = circle2.m_position.y - (circle2.m_radius * manifold.normal.y);
};
$.Engine.Collision.Collision.CollidePolyAndCircle = function (manifold, poly, circle, conservative) {
  manifold.pointCount = 0;
  var tPoint;

  var dX;
  var dY;

  // Compute circle position in the frame of the polygon.
  //var xLocal = $.Engine.Math.MulTMV(poly.m_R, b2Math.SubtractVV(circle.m_position, poly.m_position));
  var xLocalX = circle.m_position.x - poly.m_position.x;
  var xLocalY = circle.m_position.y - poly.m_position.y;
  var tMat = poly.m_R;
  var tX = xLocalX * tMat.col1.x + xLocalY * tMat.col1.y;
  xLocalY = xLocalX * tMat.col2.x + xLocalY * tMat.col2.y;
  xLocalX = tX;

  var dist;

  // Find the min separating edge.
  var normalIndex = 0;
  var separation = -Number.MAX_VALUE;
  var radius = circle.m_radius;
  for (var i = 0; i < poly.m_vertexCount; ++i) {
    //var s = $.Engine.Math.Dot(poly.m_normals[i], b2Math.SubtractVV(xLocal, poly.m_vertices[i]));
    var s = poly.m_normals[i].x * (xLocalX - poly.m_vertices[i].x) + poly.m_normals[i].y * (xLocalY - poly.m_vertices[i].y);
    if (s > radius) {
      // Early out.
      return;
    }

    if (s > separation) {
      separation = s;
      normalIndex = i;
    }
  }

  // If the center is inside the polygon ...
  if (separation < Number.MIN_VALUE) {
    manifold.pointCount = 1;
    //manifold.normal = $.Engine.Math.MulMV(poly.m_R, poly.m_normals[normalIndex]);
    var tVec = poly.m_normals[normalIndex];
    manifold.normal.x = tMat.col1.x * tVec.x + tMat.col2.x * tVec.y;
    manifold.normal.y = tMat.col1.y * tVec.x + tMat.col2.y * tVec.y;

    tPoint = manifold.points[0];
    tPoint.id.features.incidentEdge = normalIndex;
    tPoint.id.features.incidentVertex = $.Engine.Collision.Collision.nullFeature;
    tPoint.id.features.referenceFace = $.Engine.Collision.Collision.nullFeature;
    tPoint.id.features.flip = 0;
    tPoint.position.x = circle.m_position.x - radius * manifold.normal.x;
    tPoint.position.y = circle.m_position.y - radius * manifold.normal.y;
    //tPoint.position = b2Math.SubtractVV(circle.m_position , b2Math.MulFV(radius , manifold.normal));
    tPoint.separation = separation - radius;
    return;
  }

  // Project the circle center onto the edge segment.
  var vertIndex1 = normalIndex;
  var vertIndex2 = vertIndex1 + 1 < poly.m_vertexCount ? vertIndex1 + 1 : 0;
  //var e = b2Math.SubtractVV(poly.m_vertices[vertIndex2] , poly.m_vertices[vertIndex1]);
  var eX = poly.m_vertices[vertIndex2].x - poly.m_vertices[vertIndex1].x;
  var eY = poly.m_vertices[vertIndex2].y - poly.m_vertices[vertIndex1].y;
  //var length = e.Normalize();
  var length = Math.sqrt(eX * eX + eY * eY);
  eX /= length;
  eY /= length;

  // If the edge length is zero ...
  if (length < Number.MIN_VALUE) {
    //d = b2Math.SubtractVV(xLocal , poly.m_vertices[vertIndex1]);
    dX = xLocalX - poly.m_vertices[vertIndex1].x;
    dY = xLocalY - poly.m_vertices[vertIndex1].y;
    //dist = d.Normalize();
    dist = Math.sqrt(dX * dX + dY * dY);
    dX /= dist;
    dY /= dist;
    if (dist > radius) {
      return;
    }

    manifold.pointCount = 1;
    //manifold.normal = $.Engine.Math.MulMV(poly.m_R, d);
    manifold.normal.Set(tMat.col1.x * dX + tMat.col2.x * dY, tMat.col1.y * dX + tMat.col2.y * dY);
    tPoint = manifold.points[0];
    tPoint.id.features.incidentEdge = $.Engine.Collision.Collision.nullFeature;
    tPoint.id.features.incidentVertex = vertIndex1;
    tPoint.id.features.referenceFace = $.Engine.Collision.Collision.nullFeature;
    tPoint.id.features.flip = 0;
    //tPoint.position = b2Math.SubtractVV(circle.m_position , b2Math.MulFV(radius , manifold.normal));
    tPoint.position.x = circle.m_position.x - radius * manifold.normal.x;
    tPoint.position.y = circle.m_position.y - radius * manifold.normal.y;
    tPoint.separation = dist - radius;
    return;
  }

  // Project the center onto the edge.
  //var u = $.Engine.Math.Dot(b2Math.SubtractVV(xLocal , poly.m_vertices[vertIndex1]) , e);
  var u = (xLocalX - poly.m_vertices[vertIndex1].x) * eX + (xLocalY - poly.m_vertices[vertIndex1].y) * eY;

  tPoint = manifold.points[0];
  tPoint.id.features.incidentEdge = $.Engine.Collision.Collision.nullFeature;
  tPoint.id.features.incidentVertex = $.Engine.Collision.Collision.nullFeature;
  tPoint.id.features.referenceFace = $.Engine.Collision.Collision.nullFeature;
  tPoint.id.features.flip = 0;

  var pX, pY;
  if (u <= 0.0) {
    pX = poly.m_vertices[vertIndex1].x;
    pY = poly.m_vertices[vertIndex1].y;
    tPoint.id.features.incidentVertex = vertIndex1;
  }
  else if (u >= length) {
    pX = poly.m_vertices[vertIndex2].x;
    pY = poly.m_vertices[vertIndex2].y;
    tPoint.id.features.incidentVertex = vertIndex2;
  }
  else {
    //p = b2Math.AddVV(poly.m_vertices[vertIndex1] , b2Math.MulFV(u, e));
    pX = eX * u + poly.m_vertices[vertIndex1].x;
    pY = eY * u + poly.m_vertices[vertIndex1].y;
    tPoint.id.features.incidentEdge = vertIndex1;
  }

  //d = b2Math.SubtractVV(xLocal , p);
  dX = xLocalX - pX;
  dY = xLocalY - pY;
  //dist = d.Normalize();
  dist = Math.sqrt(dX * dX + dY * dY);
  dX /= dist;
  dY /= dist;
  if (dist > radius) {
    return;
  }

  manifold.pointCount = 1;
  //manifold.normal = $.Engine.Math.MulMV(poly.m_R, d);
  manifold.normal.Set(tMat.col1.x * dX + tMat.col2.x * dY, tMat.col1.y * dX + tMat.col2.y * dY);
  //tPoint.position = b2Math.SubtractVV(circle.m_position , b2Math.MulFV(radius , manifold.normal));
  tPoint.position.x = circle.m_position.x - radius * manifold.normal.x;
  tPoint.position.y = circle.m_position.y - radius * manifold.normal.y;
  tPoint.separation = dist - radius;
};

$.Engine.Collision.Collision.TestOverlap = function (a, b) {
  var t1 = b.minVertex;
  var t2 = a.maxVertex;
  //d1 = b2Math.SubtractVV(b.minVertex, a.maxVertex);
  var d1X = t1.x - t2.x;
  var d1Y = t1.y - t2.y;
  //d2 = b2Math.SubtractVV(a.minVertex, b.maxVertex);
  t1 = a.minVertex;
  t2 = b.maxVertex;
  var d2X = t1.x - t2.x;
  var d2Y = t1.y - t2.y;

  if (d1X > 0.0 || d1Y > 0.0)
    return false;

  if (d2X > 0.0 || d2Y > 0.0)
    return false;

  return true;
};
